1,721,281 research outputs found
International Symposium on a World of Wireless, Mobile and Multimedia Networks, 2006. WoWMoM 2006. Proceedings.
No full textQoS Provided by the IEEE 802.11 wireless LAN to Advanced Data Applications: a Simulative Analysis
No full textIEEE 802.11 is a Media Access Control (MAC) protocol which has been standardized
by IEEE for Wireless Local Area Networks (WLAN). The IEEE 802.11 MAC protocol
offers two types of services to its users: synchronous and asynchronous. This paper
presents an in depth analysis, by simulation, of the asynchronous part alone. The
analysis is performed by considering station data traffic patterns (hereafter advanced
data traffic) which have a very similar shape to traffic generated by WWW applications.
We carried out the simulation by taking into consideration two classes of scenarios:
balanced and unbalanced. In the former class each station has the same offered load
while in the latter class a specific station is more loaded than the others. Our conclusion
is that the IEEE 802.11 MAC protocol performs satisfactorily for both classes of
scenarios, although performance measures with advanced traffic are worse than the
corresponding performance measures with Poissonian traffic. Furthermore, we
broadened our analysis to include higher medium capacities than those planned (i.e., 1
and 2 Mbit/sec) up to 10 Mbit/sec. This part of the analysis shows that the IEEE 802.11
MAC protocol is not adequate to work at speeds planned for the forthcoming ATM
Wireless LAN
On the Structuring of Reliable Multicast Protocols for Mobile Wireless Computing
No full textWe consider reliable multicast in distributed systems including mobile hosts (MHs) that
communicate with a wired infrastructure by means of wireless links. Nearly all existing proposals
are based on hand-off, i.e. whenever a MH switches cell, state information about this host travels
across the wired network from the support station of the old cell to that of the new cell. However, we
are not aware of any detailed performance analysis for hand-off based reliable multicast protocols:
previous research in this area has focused mainly on correctness rather than on performance.
We analyze in detail, by simulation, the performance of a proposal by Acharya and Badrinath
that is based on hand-off and has been highly influential in the design of later protocols. Then, we
compare this proposal with one by us that is based on an entirely different philosophy and is the
only existing proposal not based on hand-off. Surprisingly, we found that our proposal outperforms
the one by Acharya and Badrinath in all the aspects considered: latency, scalability, bandwidth
usage efficiency and quickness in managing cell switches of MHs. Moreover, we found that this
performance improvement is not obtained at the expense of increased resource requirements on
MHs such as energy or memory. We believe that this performance and cost analysis allows us to
gain insights into the design of reliable multicast protocols for distributed mobile systems
Performance Evaluation of a MetaRing MAC Protocol Carrying Asynchronous Traffic
No full textThis paper analyzes in depth the asynchronous part of the MetaRing MAC protocol by considering a network configuration (hereafter scenario) in which the slot reuse capability is used to the minimum extent possible. The MetaRing MAC protocol behavior is first analyzed in asymptotic conditions (i.e., when each station is trying to seize all the medium capacity), then in underload conditions (i.e., when the offered load is lower than the maximum achievable aggregate throughput), and finally in overload conditions (i.e., when the offered load is slightly higher than the maximum achievable aggregate throughput). Our results show that the MetaRing is unfair and that the unfairness depends, in particular, upon the workload parameters, in addition to the K and L protocol parameter values. Our analysis includes medium capacities in the range 150 Mbps-2.4 Gbps
Wireless Sensor and Actuator Networks for Energy Efficiency in Buildings,
No full textResidential and business buildings account for a
very large fraction of the world-wide energy consumption. To
improve their energy efficiency, building management systems
(BMS) – based on (wireless) sensor and actuator networks –
have been proposed. To be effective a BMS must be responsive,
robust and scalable. Since its performance is mainly
determined by the underlying sensor and actuator network, in
this paper we focus on the communication between sensors and
actuators. Specifically, to minimize congestion, latency and
energy consumption, we propose a de-synchronization
algorithm that is able to arrange, dynamically, periodic
transmissions from different sensor nodes in a round-robin
collision-free style, like in conventional TDMA. Unlike TDMA,
however, it does not require synchronization, and is able to
adapt to changes in the network topology. Our preliminary
results show that the proposed algorithm converges to a
steady-state in a limited number of periods
Delay Analysis of a Worst-case Model of the MetaRing MAC Protocol with Local Fairness
No full textThe MetaRing is a medium access control (MAC) protocol for gigabit LANs and MANs with cells removed by the destination stations (slot reuse). Slot reuse increases the aggregate throughput beyond the capacity of single links but may cause starvation. In order to prevent this the MetaRing MAC protocol includes a fairness mechanism. Two types of fairness algorithms have been proposed: 'global' and 'local'. The MetaRing analysed in this paper implements the local fairness algorithm specified in [2]. In order to reduce the complexity we have identified a simplified model which can be analytically solved and yet still provides useful information on network performances. This model represents a worst-case scenario in which network congestion is stressed, i.e. no station, apart from a specific station (tagged station), ever has an empty queue. The model proposed can be represented by a discrete time discrete state Markov chain of M/G/1-type and hence the matrix analytical methodology has been used to solve it. Our analysis focuses on the average access delay experienced by the tagged station as a function of the offered load. The results show that average access delay remains bounded for values of offered load less than or equal to 90%. Furthermore, the average access delay depends on the number of interfering stations and on the protocol parameter Qr
Extending the Lifetime of Wireless Sensor Networks through Adaptive Sleep
No full textIn recent years, the use of wireless sensor networks for industrial applications has rapidly increased. However, energy consumption still remains one of the main limitations of this technology. As communication typically accounts for the major power consumption, the activity of the transceiver should be minimized, in order to prolong the network lifetime. To this end, this paper proposes an Adaptive Staggered sLEEp Protocol (ASLEEP) for efficient power management in wireless sensor networks targeted to periodic data acquisition. This protocol dynamically adjusts the sleep schedules of nodes to match the network demands, even in time-varying operating conditions. In addition, it does not require
any a priori knowledge of the network topology or traffic pattern. ASLEEP has been extensively studied with simulation. The results
obtained showthat, under stationary conditions, the protocol effectively reduces the energy consumption of sensor nodes (by dynamically adjusting their duty-cycle to current needs) thus increasing significantly the network lifetime.With respect to similar nonadaptive solutions, it also reduces the average message latency and may increase the delivery ratio. Under time-varying conditions, the protocol is able to adapt the duty-cycle of single nodes to the new operating conditions, while keeping a consistent sleep schedule among sensor nodes. The results presented here are also confirmed by an experimental evaluation in a real testbed
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